1. Field of the Invention
The invention is situated in the field of materials handling technology and it relates to a method and a device for transporting articles along a conveying track, wherein the articles are held individually and are transported along the conveying track one behind the other and at least to a limited extent independent of one another and wherein the articles pass through an accumulation store during the transportation along the conveying track.
2. Description of Related Art
Conveyance according to the manner mentioned above is known in particular for flat articles, such as newspapers and periodicals, from the publications DE-2822060 (or U.S. Pat. No. 4,201,286), CH-382768 (or U.S. Pat. No. 3,032,341) EP-0276409 (or U.S. Pat. No. 4,892,186), EP-0309745 (or U.S. Pat. No. 4,887,809) or WO-99/33731 (or U.S. Pat. No. 6,357,574). For such transport, each one of the flat articles is conveyed while being held by a holding element such that its principal surfaces are oriented substantially transverse to the conveying direction. The holding elements are movable individually and at least to a limited extent independently of one another along a stretch of rails and they are designed such that they can be driven pushing one another. The dimension of the holding elements parallel to the conveying direction is the same for all holding elements and is advantageously greater than the corresponding dimension of the articles (thickness of the flat articles), so that in pushed operation there are defined distances between holding elements (e.g. distance between the front ends of successive holding elements) or between articles held by the holding elements respectively, which distances in a given system are the smallest possible distances.
In comparison with conveying methods using holding means being arranged equidistantly on a single conveying organ, e.g. on a circulating chain, the conveying methods for flat articles as described in brief above has, inter alia, the following advantages: the distances between the holding elements can be changed locally and independent of one another by very simple means and in particular without transfer of the articles to other holding means; very dense and nonetheless very precisely arranged conveying streams can be formed; and conveying tracks can be designed as accumulation store devices in a very simple manner.
For the formation of an accumulation store, the holding elements are solely banked up along the conveying track, are released from the head of the banked up articles in a controlled manner, and are conveyed onwards. The group of banked up articles, which has a stationary head and a variable length, represents the accumulation store. For realizing such an accumulation store on a conveying track, drives (motor drives or the force of gravity) are to be provided for conveying holding elements with a constant or variable speed and with constant or variable spacings to the tail end of the accumulation store and with variable speed and minimum distances between one another through the accumulation store (supply drive and buffer drive), and for conveying holding elements to be released at the buffer head away from the accumulation store (conveying-away drive). Furthermore, means for banking up holding elements in the accumulation store for releasing them from the accumulation store and for transferring them to the conveying-away drive are to be provided.
Accumulation stores are utilized wherever a unit supplying articles and a unit taking over the articles are to be connected with one another in a flexible manner, such that the units can be operated with respect to their performance (measured in articles per unit of time) within wide limits without any mutual interdependences (uncoupled), and nonetheless without the necessity to take the articles out of a common process-order. When the performance of the unit supplying the articles is greater than that of the unit taking over the articles, the fill level of the accumulation store increases. When the performance of the unit supplying the articles is smaller than the performance of the unit taking over the articles, then the fill level of the accumulation store decreases.
In accordance with the prior art (refer to the publications mentioned above), accumulation stores on conveying tracks equipped for held and independent transportation of holding elements or of articles held by holding elements, respectively, the banking-up means or releasing means respectively comprise a timing wheel arranged at a stationary head of the store. This timing wheel comprises teeth adapted to the holding elements and in rotation it grasps with each of its teeth the respectively first holding element in the accumulation store, in order to separate it from the head of the accumulation store and to transfer it to the conveying-away drive. For a variable release performance (in holding elements or held articles per unit of time) the speed of rotation of the timing wheel is varied as required or the timing wheel is switched (predefined, non-variable speed or standstill).